Possible speculations are:
- There are errors in offers, which they'd like to avoid next time. For example random manager assignments etc.
- The offer/portal/FAQ asks people to reject offer (by resigning) and yet be subject to severance pay. Yet, the severance pay available is only US specific. This could lead to legal issues, since you're asking for people to quit based on something that doesn't exist.
- There are no more offers to give out. The next batch is severance offer. It would help if the severance plan is available across all geographies.
- Broadcom/VMW are incompetent.
- Other reasons.